Correlation functions for orbifolds of the type M-N/S-N

The D1-D5 system, which arises in black hole physics, gives rise to a 2-d C FT which is the low energy limit of a sigma model with target space an orbi fold (M-4)(N) / S-N. (M-4 is a 4-d manifold which can be T-4 or K3, and S-N is the permutation group on N elements). With this motivation, we develop a method for computing correlation functions of twist operators in the boso nic 2-d CFT arising from orbifolds M-N / S-N, where AT is an arbitrary mani fold. We find intriguing relations between the CFT correlators and the grav ity theory that is conjectured to be dual to the D1-D5 system.